We certainly already know the upfront costs of establishing a colony as given by the costs of the Civilian Infrastructure upgrades, which are as follows:
Lv 1: 450cr, 150m, 75c
Lv 2: 550cr, 175m, 125c
Lv 3: 650cr, 200m, 175c
Lv 4: 750cr, 225m, 225c

On the basis that 1 metal/crystal = 4.5 credits (the average cost of buying metal/crystal on the Black Market), then the equivalent credit cost for each of the four levels are:
Lv 1: 1462.5cr
Lv 2: 1900cr (cumulatively 3362.5cr)
Lv 3: 2337.5cr (cumulatively 5700cr)
Lv 4: 2775cr (cumulatively 8475cr)

These numbers, clearly, are only representative numbers - what 1 credit for us is equivalent to for a civilian is up for us to interpret. Certainly a credit for the player probably represents a vast amount of wealth given how expensive it is to construct ships and structures.

We could also suppose that the cost of maintaining a colony is given by the underdevelopment tax associated with newly established colonies. IIRC, the UD Tax for Terran planets with level 1 CI is 2.3cr/second (I can't recall the UDT for level 2). One could consider this tax to be cost of maintaining the colony - at higher levels, it is able to sustain itself and does not need outside assistance.

You will be able to tell when you see questions like how does a smurf pilot a capital ship if he cant reach the controls? or how do smurfs populate a planet with only 1 female? how about if a billion smurfs are on a desert planet, will it be blue from space?

good one

Again, probably the costs of the CI upgrades will give a clue, seeing as the cost of new infrastructure is the same, whether the colony had been previously bombed or not.

 First off, happy Friday!

Second, I'm going to use a part of one of Uranium - 235's reply to the Conquering Planet:why only bombardment thread to help get the gist of my question:"It's infrastructure, that's what the upgrades are called. When you're dropping bombs in the upper megaton range like the TEC are doing, you're wiping out that infrastructure. You've not only uprooted the government, you've displaced millions of people (certainly killed quite a few, too). You have refugees in camps, their cities are full of insurgents, rioting, and anarchy. When you first take over, your government only controls a small part of that planet, a "green zone". It's taking a lot of money to deal with the starving population who are lacking proper hospital care, food, water, and power. These people need to get back to their homes in the cities, and that's where spending money on relocation, reconstruction." So,here's my question: Why would it realistically cost so much to relocate the refugees back to the cities?

 In the Trinity manual , under the Starting A New Empire section, it mentions: "Make sure to build out the population centers of any new planet you acquire. You'll lose money until you do so and you won't last long with the credits draining from your economy." as an explanation for the Underdevelopment Tax, so here's my question: why would un-upgraded native population centers be a drain on your credit income?

 I'll continue from my last post, most of the planets you can colonize are inhabitable and have native populations, therefore, they would have their own developed infrastructure, including energy creation and distribution and agriculture when you first colonize. They would have their own cities and their own government, so why would you have build out the native population centers when there already developed?

Now I can understand the Underdevelopment Tax for the Vasari with them being an entirely different Race and all, the TEC and the Advent are physiologcally Human.

Population centers not big enough... native population unwilling to work with your empire... etc.

Physiology has absolutely nothing to do with development costs outside of the shape or the size of things, and you're over estimating the ability of native populations with no real financing or capital improvement funding backing them.  If you look at the planets, there are NO cities on them until after you colonize.  They may have some infrastructure and form of government for their little piece of the world, but there's nothing even remotely close to the global scale that you, the player, has to deal with.  The manual also states that the Vasari enslave other races and generally rule from orbit, so in that sense, their faction has no development costs tied to their personal comforts.

Here's the thing, the Sins universe that we play in assumes that all planets have some native human populations since it's been thousands of years since mankind has reached out for the stars, and that a large part of humanity has the ability to pack up and move to a new planet just as easily as it is for you and I to pack up and move to a new home, maybe even easier...  Now in game terms, this is my impression of what happens based on what I see in the game itself, and what I've read in the manual and other places:

(Initial Colonization)
When a new government comes in, you have to do things to appease the populace and get them to support you and get them to move to urban centers.  If you look at a planet in the game, there are no cities.  Once you colonize it, a few appear.  In real life, having a city of 1 million people in a location that's only a few hundred square miles is much more profitable then having that same million people spread out over a million square miles.  It's much easier and much more profitable to govern the City of New York then it is to govern the entire State of Virginia.  Roughly the same amount of people, far smaller space.  Build a lot of stuff close together and people don't have to go very far for anything.  You spend less on building and maintaining power transmission lines, you spend less on building and maintaining water / sewer lines, you spend less on building and maintaining transportation networks.  People tend to like not having to drive 30 miles to buy groceries.  People tend to like having schools and fire stations and hospitals nearby.  As the population of the planet climbs in the game, you see more urban centers appearing.  The more you fund into building up, the more people you can entice to come and live on your planet.  Failing to fund new urban centers means you waste money providing services to a much wider area.  Providing medical services or fire protection or police protection, for example, costs a lot more in the countryside then it does in the city on a per capita basis.  The reason?  Distance.  Plain and simple as that.  Roads in the countryside have to stretch for miles sometimes just to link a few homesteads together.  In the city, a few dozen feet of road does the same thing.  It costs a hell of a lot more to maintain miles of road then it does a few dozen feet.  There's your underdevelopment tax.  You fail to fund and develop the urban centers, you pay to have to cover long distances for everything.

(Planet Bombardment)
This aspect effectively means you're bombing those urban centers and scattering the people across the globe and demoralizing them as much as possible.  You're targeting the tallest buildings, the government facilities, important monuments, i.e. if you were to attack the US from space, you wouldn't shoot at the middle of Nebraska, you'd shoot at Washington DC and go after the head of the government, you'd bomb New York, Los Angeles, Chicago, Dallas, Atlanta, etc. and get people to leave and spread out thus making them much harder to protect and control.  You'd bomb Mount Rushmore, the Golden Gate Bridge, and Cape Canaveral and remove the things that make people proud to be who they are, and you keep on bombing until they've given up all hope that their current governors can protect and provide for them.  In the game, as the population numbers drop, you'll see those urban centers start to disappear.  Keep on bombing and you'll eventually destroy all of the large urban centers and emergency shelters.

(Re-Colonization)
As in the initial colonization phase, you're primary focus is rebuilding.  Rebuilding new infrastructure, rebuilding new urban centers, rebuilding new governments, rebuilding new monuments...  Just because someone did this before, doesn't mean it's going to be cheaper for you to redo it after you've blown it all up.  If anything, it's typically more expensive because you have the added cost of cleaning up your mess before you can get started on rebuilding.  So while you may not have to pay for new everything as the first colonizer did, you're footing the bill for cleaning up as well, or as the case may be, footing the bill for the added cost to the population for failing to clean up.  As in the initial colonization phase, you're being taxed because the people are scattered and you have to pay to cover their needs over longer distances.  Once you start funding those urban centers, more people move to them, reducing that distance cost.  More people move to the planet and you get more tax money out of it.

(Failed Bombardment)
Granted, during bombardment, the population got scattered and some or all of their urban centers destroyed, but if you had spent the money on building emergency shelters to protect the populace from that bombardment, they can bounce back, rebuild, and repopulate urban centers quickly.  While this process is going on, they still have places to live and go about their daily lives and your government still has a place to rule from.  Your costs remain the same (meaning you're not being taxed) because you've thought ahead and planned for this eventuality.  While the population is more scattered then if they were in large urban centers, their basic needs are still being provided for them collectively.  So obviously, you're not collecting the taxes you normally would as the population rebuilds, but eventually, life returns to normal, those urban centers are rebuilt and repopulated, and you return to collecting your credits which the people should be happy to be paying because that's what's protecting their collective butts.

(Abandonment)
Oddly enough, there are times where ditching a planet is smarter then continually sinking money into it.  If it's a frequent target, if it's just got too many ways to access forcing you to hold a portion of your fleet back for protection, if you want to give it to an ally...  Those aren't the only reasons, but sometimes it's just better to walk away from it.  While you're doing this, technically, you're cutting off access to the urban centers you've built up, letting them fall into disrepair, or general neglect.  Whatever is actually happening, the safe thing to assume is you're yanking your government out.  You're making your people bail on the population, and maybe once the government is gone, martial law takes effect and the planet's own little defense force scatters the population intentionally so that there's less chance for large groups to get together and riot or become a serious threat to safety.  Maybe there isn't a planetary police force, and maybe the population does destroy everything in their lawless environment.  It really doesn't matter what's actually happening because it's the next owner's problem to worry about.  Because it's not your problem, there's no cost to you unless you decide you want to recolonize, then you have to start all over again.

Well, yes, you do see lights.  The dark side texture for a planet has lights on it and those never change.  It never changes.  It's a picture.  If you'd like, I can create dark side textures for you that have no lights, I could also create dark side textures that have a lot more lights.  I don't disagree that there aren't large gatherings of dwellings that are able to put off enough light that it can be seen from space...  In fact, it doesn't require a whole lot of light to make that happen.  Townships of about 100 structures can be seen from space if they have what the average person would consider to be proper lighting at night.

Look at this picture of Europe, particularly take note of the lights you can see in Africa in the central part of the picture at the bottom.  Notice that you can see Russia just littered with light.  Mind you, that area near the edge of the visible part of the Earth is Siberia and not much exists out there, yet at night, all of those areas light up quite well.  Granted, they're nothing compared to the clusters of lights that you can see where the cities of Madrid, Paris, London, Rome, or Athens are...

However, what I'm referring to the actual graphics of buildings that are added along with the 'traffic' flying between them while the planet is colonized.  Those are the real cities / large urban centers.  Those are the ones that are added as the population climbs and explode while the planet is being attacked and the population declines.  Let's not pick apart trivial details.

Yikes mate... its a game, not complete reality where everything is utterly perfect under the laws of physics and anthropoligical/extraterrestrial behavioral science!

Enjoy the flashing lights and explosions...  

lmao